Circular saw

Abstract

A circular saw comprises a housing, a driving unit contained in the housing, a saw blade driven to rotate to cut a workpiece, a speed reduction mechanism installed between the driving unit and the saw blade for changing the rotation speed of the saw blade, and a saw blade guard; the housing comprises a gear box that at least partially contains the speed reduction mechanism, and the gear box is provided with at least one vent hole. According to the circular saw of the present invention, it is possible to effectively suppress the expansion of air in the gear box and prevent the lubricant encapsulated in the gear box from leaking and causing the saw blade guard to become stuck, thereby improving the safety, quality and durability of the circular saw.

Description

Technical Field

[0001] The invention relates to a power tool, in particular to a circular saw. Background Art

[0002] A circular saw is a widely used power tool for cutting workpieces such as wood, metal and many other materials.

[0003] A circular saw generally includes a driving unit disposed in a housing, a gear shaft connected to the driving unit, and a saw blade mounted on the gear shaft. The driving unit, such as a motor, includes a driving shaft that meshes with the gear shaft in a gear box of the circular saw. The gear meshing mechanism here is a speed reduction mechanism for changing the rotation speed of the saw blade. When the motor starts to operate, the driving shaft drives the gear shaft to rotate, and the saw blade is driven to rotate with the gear shaft, thereby achieving cutting of the workpiece. A circular saw generally also includes a handle disposed on the housing, a support plate that contacts the workpiece during the cutting operation, an upper protective cover, and a rotatable saw blade guard. The rotatable saw blade guard can rotate around the rotation axis of the saw blade between its closed position and the working position, and can prevent the rear side of the high-speed rotating saw blade from accidentally contacting the user during the saw blade cutting the workpiece, and also protect the user from flying chips separated from the workpiece during the cutting process.

[0004] Usually, a certain amount of lubricant needs to be added to the gearbox to lubricate the gears during the gear meshing process. The lubricant used is generally a soft, thick, grease-like semi-solid grease, so the gearbox needs to have good sealing performance to prevent the grease from leaking out of the gearbox. In order to achieve high sealing performance, a variety of sealing components can be provided, such as O-rings, oil seals, contact seal bearings, etc.

[0005] However, during the operation of the circular saw, the speed reduction mechanism in the gearbox will generate heat due to high-speed rotation, causing the temperature inside the sealed gearbox to increase and the air inside the gearbox to expand. In this case, a vent is required to allow the high-temperature air in the gearbox to be discharged. At the same time, the grease in the gearbox is generally evenly distributed in the gearbox when the circular saw is in operation, and there is also the possibility of leakage from the vent. Moreover, the semi-solid grease may be partially liquefied under the action of high-temperature and high-pressure gas, and may also leak from the vent. The grease leaked from the gearbox accumulates in the gap between the bearing cover of the gear shaft and the mounting ring of the saw blade guard after cooling. Since a small amount of dust or flying chips will fall into the gap during the saw blade cutting the workpiece, the solid grease mixed with the dust or flying chips will affect the normal rebound or bias of the saw blade guard to the closed position, resulting in safety hazards. Summary of the invention

[0006] The object of the present invention is to provide a circular saw which can effectively suppress the expansion of air in a gear box and prevent the leakage of lubricant encapsulated in the gear box from causing the saw blade guard to become stuck, thereby improving the safety, quality and durability of the circular saw.

[0007] A circular saw comprises a housing, a driving unit contained in the housing, a saw blade driven to rotate to cut a workpiece, a speed reduction mechanism installed between the driving unit and the saw blade for changing the rotation speed of the saw blade, and a saw blade guard; the housing comprises a gear box that at least partially contains the speed reduction mechanism, and the gear box is provided with at least one vent hole. The vent hole provided in the gear box can discharge high-temperature and high-pressure gas caused by the operation of the speed reduction mechanism during the operation of the circular saw.

[0008] According to one embodiment of the present invention, the drive unit includes a motor having a drive shaft, the reduction mechanism includes a gear shaft that defines the rotation axis of the saw blade, the gear shaft is constructed with one end being an input end connected to the drive shaft of the motor by gear meshing, and the other end being an output end supporting the saw blade, the gear box has a bearing seat for accommodating the drive shaft on the side facing the drive unit, and has a recess for accommodating the input end of the gear shaft on the side facing the saw blade, the bearing seat and the recess are at least partially connected, and the saw blade guard is mounted on the output end of the gear shaft, and can rotate around the rotation axis of the saw blade between its working position and a closed position.

[0009] According to a preferred embodiment of the present invention, the recess includes a side circumference substantially parallel to the rotation axis of the saw blade and a bottom surface substantially perpendicular to the rotation axis of the saw blade, and the vent hole is located on the bottom surface of the recess. In this way, when a small amount of semi-solid grease pre-packaged in the gear box leaks from the vent hole, the grease is discharged from the inner side of the gear box (the side facing the gear shaft, the saw blade and the saw blade guard) through the vent hole to the outer side of the gear box (i.e., the side facing away from the gear shaft, the saw blade and the saw blade guard), so there is no jamming caused by the accumulation of a mixture of grease, dust and flying chips in the gap between the saw blade guard and the bearing cover, ensuring that the saw blade guard can rotate normally between the working position and the closed position.

[0010] Preferably, the bottom surface of the recess is substantially circular, and the center of the bottom surface coincides with the rotation axis of the saw blade. The position of the vent on the bottom surface is higher than the horizontal plane extending along the rotation axis of the saw blade. When the circular saw is not in operation, the grease in the gear box tends to be concentrated in the lower half of the gear box. Therefore, the vent is set at a height exceeding the center of the bottom surface, which is conducive to preventing the grease from leaking from the gear box.

[0011] According to another preferred embodiment of the present invention, the input end of the gear shaft has a transmission gear and a journal, the side circumference of the recess substantially surrounds the transmission gear, the bottom surface of the recess is provided with a bearing hole supporting the journal at its center, and the distance from the vent hole to the center of the bottom surface is less than the root circle radius of the transmission gear. The vent hole is below the transmission tooth, which is also conducive to preventing excessive leakage of grease.

[0012] According to another preferred embodiment of the present invention, the angle between the radius of the vent hole on the bottom surface and the vertical direction is smaller than the angle between the radius of the center line of the drive shaft and the vertical direction. In other words, the vent hole is located in the upper half of the bottom surface close to the vertical sector area passing through the center of the bottom surface, so that high-pressure and high-temperature air can be effectively discharged, and grease can be prevented from leaking out of the gear box in large quantities or even completely from the vent hole, thereby ensuring that a sufficient amount of grease is retained in the gear box, and the speed reduction mechanism is always fully lubricated within the service life of the circular saw.

[0013] The end of the driving shaft has a driving gear, a bearing is sleeved on the driving shaft, the bearing seat includes a hole for supporting the bearing and a cavity for accommodating the driving gear which at least partially overlaps with the recess along the axial direction, a plurality of reinforcing ribs are arranged at the periphery of the hole, and the position of the vent hole avoids the reinforcing ribs. In this way, the processing technology of the vent hole is simple and convenient, and the ventilation and exhaust effect is better.

[0014] More preferably, the vent hole is obliquely arranged on the bottom surface, and the end of the vent hole facing the gear shaft is closer to the center of the bottom surface than the other end facing away from the gear shaft. The obliquely arranged vent hole has a longer exhaust path. The vent hole is inclined radially outward from the side close to the bearing hole to the side close to the transmission tooth, so that the semi-solid or partially liquefied grease is less likely to leak from the gear box to the outside of the gear box.

[0015] According to another preferred embodiment of the present invention, the vent hole is a through hole with a diameter not greater than 2 mm. The vent hole should be as small as possible, but considering the convenience of machining and cost factors, a circular hole with a diameter not greater than 2 mm is preferred. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The embodiments can be better understood by reading the accompanying drawings while describing the following in detail. It is emphasized that the various components are not necessarily drawn to scale. In fact, the dimensions may be increased or decreased arbitrarily for clarity of discussion. In the accompanying drawings, the same reference numerals refer to the same elements.

[0017] Figure 1 A partial schematic diagram showing a circular saw according to an embodiment of the present invention;

[0018] Figure 2 yes Figure 1 A partial perspective view of a circular saw according to one embodiment of the present invention is shown;

[0019] Figure 3 is a cross-sectional view of an exemplary drive unit and a speed reduction mechanism of a circular saw of the present invention arranged in a gear box;

[0020] Figure 4 A schematic diagram showing a side of an exemplary gear box of a circular saw of the present invention facing the saw blade;

[0021] Figure 5 yes Figure 4 A partial enlarged schematic diagram of the gearbox at position C shown;

[0022] Figure 6 yes Figure 3 A schematic diagram of the gearbox shown facing the drive unit side;

[0023] Figure 7 yes Figure 6 A partial enlarged schematic diagram of the gearbox at point B is shown. DETAILED DESCRIPTION

[0024] Next, we will refer to Figures 1 to 7 A circular saw according to an embodiment of the present invention is described. The present invention relates to a circular saw, which is used to form an opening in a workpiece and is widely used for cutting workpieces, such as wood, vinyl siding and many other materials, and is also used for cutting metal parts. The "circular saw" mentioned in the present invention can be a circular saw used for woodworking, metalworking, ceramic processing, and / or plastic processing, in which a rotating saw blade cuts the workpiece. Portable circular saws or table circular saws are also included in the "circular saw" mentioned here. In addition, the "circular saw" also includes a cutting saw, a band saw, a cutting grinding wheel, a diamond grinding wheel, etc. In addition, the "power source" of the power tool mentioned in the present invention is typically an electric motor, and also includes pneumatic motors, engines, etc.

[0025] According to an exemplary embodiment of the present invention, Figures 1 to 3 As shown, the circular saw 1 includes a housing 10, a driving unit 11 accommodated in the housing 10 and supported by the housing, a saw blade 12 driven to rotate to cut a workpiece, a reduction mechanism 13 installed between the driving unit and the saw blade for changing the rotational speed of the saw blade, an upper protective cover 14, and a saw blade guard 15. The housing 10 also includes a gear box 16 that at least partially accommodates the reduction mechanism 13.

[0026] The housing 10 can be formed of metal or plastic, making the housing 10 very strong and light. In one embodiment of the present invention, the upper cover 14 is supported by the housing 10 and fixed in a proper position relative to the housing 10 , and the upper cover 14 substantially covers the upper half of the circumference of the saw blade 12 .

[0027] See also Figure 2 and Figure 3 According to one embodiment of the present invention, the drive unit 11 can be powered by a battery (not shown), or can be powered by a wired power supply as known in the art. The drive unit 11 includes a drive motor 18, a drive shaft 19, and a drive bearing 20. The drive bearing 20 is sleeved on the drive shaft 19, and the end of the drive shaft 19 has a drive gear 21.

[0028] According to one embodiment of the present invention, the speed reduction mechanism 13 is configured to reduce the output speed of the motor 18 to a speed suitable for rotating the saw blade 12. According to an exemplary embodiment of the present invention, the speed reduction mechanism includes a gear shaft 22, one end of which is an input end 23 connected to the drive shaft 19 of the motor by gear meshing, the input end 23 having a transmission gear 24 and a journal 32 extending axially outward, and the other end is an output end 25 supporting the saw blade 12. The gear shaft defines the rotation axis 17 of the saw blade, that is, the rotation center of the output end of the gear shaft coincides with the rotation axis 17 of the saw blade. When the motor 18 is energized, the drive shaft 19 drives the transmission gear 24 of the gear shaft 22 to rotate through the drive gear 21, and the saw blade 12 rotates around the rotation axis 17 with the gear shaft 22. In an alternative embodiment, the speed reduction mechanism may include a plurality of gear meshing transmission mechanisms. In other exemplary embodiments, the speed reduction mechanism may also include a worm gear transmission device (not shown) for driving the gear shaft.

[0029] refer to Figures 2 to 7 The housing 10 further includes a gear box 16, which is located approximately on the back of the upper protective cover 14 ( Figure 2 and Figure 3), preferably, the gear box 16 and the upper protective cover 14 are integrally formed. According to an illustrative embodiment of the present invention, the gear box 16 is a cavity extending outward from the bottom center of the back side of the upper protective cover, and a plurality of reinforcing ribs may be provided in the cavity. The gear box 16 has a bearing seat 26 for accommodating the drive shaft on the side facing the drive unit 11, and a recess 27 for accommodating the input end 23 of the gear shaft on the side facing the saw blade, and the bearing seat 26 and the recess 27 are at least partially connected. Preferably, the bearing seat 26 includes a hole portion 33 for supporting the bearing and a cavity portion 34 for accommodating the drive gear of the drive shaft, which at least partially overlaps with the recess. In this way, the drive gear 21 of the drive shaft 19 and the transmission gear 24 of the input end 23 of the gear shaft 22 are connected in a gear meshing manner in the area where the cavity portion 34 and the recess 27 overlap.

[0030] The saw blade guard 15 is pivotally mounted on the bearing cover of the output end 25 of the gear shaft 22 via a mounting ring. The saw blade 12 is fixedly mounted on the output end 25 of the gear shaft via a mounting flange, a clamping flange, and a clamping screw. The saw blade guard 15 generally covers the lower half of the saw blade 12, and the saw blade guard 15 is configured to be able to rotate around the rotation axis 17 of the saw blade 12 between a closed position and a working position. The circular saw 1 also includes a biasing member (not shown), such as a torsional elastic element, which is configured to bias the saw blade guard 15 toward the closed position. That is, the saw blade 12 and the saw blade guard 15 are both mounted on the inner side of the gear case, i.e. Figure 2 and Figure 3 The left side of the gear box, and the drive unit 11 is located outside the gear box, that is, Figure 2 and Figure 3 on the right side of the screen.

[0031] According to a preferred embodiment of the present invention, Figures 2 to 5 The recess 27 includes a side circumference 28 substantially parallel to the rotation axis 17 of the saw blade and a bottom surface 29 perpendicular to the rotation axis 17 of the saw blade, and at least one vent hole 30 is provided on the bottom surface 29. In this way, the grease previously packaged in the gear box for lubrication can be partially discharged from the gear box through the vent hole 30 located on the bottom surface of the recess. Figure 3 The left side of the gear box is discharged to the outside of the gear box ( Figure 3 Therefore, there is no jamming caused by the mixture of grease, dust and flying debris accumulating between the gap between the saw blade guard 15 and the gear shaft bearing cover, ensuring that the saw blade guard 15 can rotate normally between the working position and the closed position.

[0032] Preferably, the bottom surface 29 of the recess is substantially circular, the center of the bottom surface coincides with the rotation axis of the saw blade, and the side circumference 28 and the bottom surface 29 form a cylindrical recess. The side circumference 28 of the recess substantially surrounds the transmission gear 24, and the bottom surface 29 of the recess is provided with a bearing hole 31 at its center for supporting the journal 32 of the gear shaft. The journal 32 of the gear shaft 22 is supported in the bearing hole 31 through a bearing, and the position of the vent hole 30 on the bottom surface is at least higher than the horizontal plane passing through the rotation axis 17 of the saw blade, where the rotation axis 17 of the saw blade coincides with the center line of the bearing hole 31. In other words, the position of the vent hole 30 on the bottom surface 29 should be located in the upper half of the bottom surface, at least higher than the horizontal plane of the center of the bottom surface. More preferably, the angle between the extended line passing through the vent hole 30 and the center of the bottom surface and the vertical direction is smaller than the angle between the extended line passing through the center of the bearing seat hole 26 and the center of the bottom surface and the vertical direction. That is to say, the position of the vent hole 30 is set in the upper half of the bottom surface near the vertical sector area passing through the center of the bottom surface. Because the grease needs to be added to the gear box in advance to lubricate the transmission of the drive shaft and the gear shaft. The filled grease needs to be applied in sufficient amount according to the service life of the circular saw to ensure good lubrication of the circular saw throughout its life cycle. However, as mentioned above, the semi-solid grease will be liquefied a small amount under high temperature and high pressure air, and the fluidity of the liquefied lubricant will increase significantly, and it may be discharged from the gear box through the vent hole. Therefore, the vent hole is set above the bearing hole, which can not only effectively discharge the high pressure and high temperature air, but also prevent the grease from leaking out of the gear box in large quantities or even completely from the vent hole, ensuring that a sufficient amount of grease is retained in the gear box, and the reduction mechanism is always fully lubricated within the service life of the circular saw.

[0033] refer to Figure 6 and Figure 7 According to another preferred embodiment of the present invention, a plurality of reinforcing ribs 35 are provided on the periphery of the hole portion 33, and the position of the vent hole 30 avoids the position of the radial reinforcing rib 35. In this way, the processing technology of the vent hole is simple and convenient, and the ventilation and exhaust effect is better. The reinforcing rib can be used to connect an air guide device 36. Since the vent hole is located in the area surrounded by the reinforcing rib, a small amount of grease leaked from the vent hole will be received by the air guide device and will not accumulate on the gear shaft or the drive unit.

[0034] Preferably, the vent hole 30 is a circular hole with a diameter not greater than 2 mm. The vent hole should be as small as possible, but considering the convenience of machining and cost factors, a circular hole with a diameter not greater than 2 mm is easy to process, while ensuring a good exhaust effect and not causing excessive grease to leak from the gear box. In fact, grease leakage from the vent hole usually only occurs at the beginning of the use of the circular saw, and the amount of grease initially packaged in the gear box is relatively high. After a period of use, the gear meshing of the reduction mechanism has been completely run-in, and the amount of grease in the gear box has gradually reached a balance value, which can ensure sufficient lubrication of the reduction mechanism without continuously leaking more from the vent hole.

[0035] More preferably, the vent hole 30 is an oblique vent hole, which is not perpendicular to the bottom surface 29 of the gear box. The oblique vent hole has a longer exhaust path. Preferably, the vent hole is inclined radially outward from the side close to the bearing hole 31 to the side close to the transmission gear 24, so that the liquefied grease is less likely to leak from the gear box to the outside of the gear box, thereby ensuring that the grease encapsulated in the gear box can always maintain sufficient lubrication for the drive unit and the reduction mechanism, thereby extending the service life of the tool.

[0036] As mentioned above, although the exemplary embodiments of the present invention have been described in the specification with reference to the accompanying drawings, the present invention is not limited to the above-mentioned specific implementation modes, and many other implementation modes may be provided. The scope of the present invention should be limited by the claims and their equivalents.

Claims

1. A circular saw, comprising a housing, a driving unit accommodated in the housing, a saw blade driven to rotate to cut a workpiece, a speed reduction mechanism installed between the driving unit and the saw blade for changing the rotation speed of the saw blade, and a saw blade guard; the housing comprises a gear box at least partially accommodating the speed reduction mechanism, characterized in that: The gear box is provided with at least one vent hole, the drive unit includes a motor with a drive shaft, the speed reduction mechanism includes a gear shaft defining the rotation axis of the saw blade, the gear shaft is configured to have one end as an input end connected to the drive shaft of the motor by gear meshing, and the other end as an output end supporting the saw blade, the gear box has a bearing seat for accommodating the drive shaft on a side facing the drive unit, and a recess for accommodating the input end of the gear shaft on a side facing the saw blade, the bearing seat and the recess are at least partially connected, the saw blade guard is mounted on the output end of the gear shaft and can rotate around the rotation axis of the saw blade between its working position and a closed position, the recess includes a side circumferential surface parallel to the rotation axis of the saw blade and a bottom surface perpendicular to the rotation axis of the saw blade, the vent hole is located on the bottom surface of the recess, the position of the vent hole on the bottom surface is higher than a horizontal plane extending along the center of the bottom surface, the vent hole is obliquely arranged on the bottom surface, and the end of the vent hole facing the gear shaft is closer to the center of the bottom surface than the other end away from the gear shaft.

2. The circular saw according to claim 1, characterized in that The bottom surface of the recess is circular, and the center of the bottom surface coincides with the rotation axis of the saw blade.

3. The circular saw according to claim 1, characterized in that The input end of the gear shaft is provided with a transmission gear, and the distance from the vent hole to the center of the bottom surface is smaller than the tooth root circle radius of the transmission gear.

4. The circular saw according to claim 3, characterized in that The angle between the radius of the bottom surface extending through the vent hole and the vertical direction is smaller than the angle between the radius of the center line extending through the drive shaft and the vertical direction.

5. The circular saw according to any one of claims 1 to 4, characterized in that The end of the driving shaft is provided with a driving gear, and a bearing is sleeved on the driving shaft. The bearing seat includes a hole portion for supporting the bearing and a cavity portion for accommodating the driving gear which at least partially overlaps with the recess along the axial direction. A plurality of reinforcing ribs are provided on the periphery of the hole portion, and the position of the vent hole avoids the reinforcing ribs.

6. The circular saw according to any one of claims 1 to 4, characterized in that The vent hole is a circular hole with a diameter not greater than 2 mm.

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